1. Field of the Invention
The present invention is related generally to bushing assemblies and more particularly to metal bushing assemblies having a stud and a housing which is rotatable relative to the stud.
2. Related Art
Many automotive vehicles today employ suspension systems commonly known as MacPherson strut systems or double-wishbone systems. Such systems typically include a lower control arm (also referred to as an A-arm) which pivots relative to the vehicle's frame to allow a wheel and tire to move upwardly and downwardly relative to the frame during cornering or in response to encountering an object, such as a pot hole in the road.
A lower control arm 10 for a Macpherson strut type of suspension system is generally shown in FIG. 1. The lower control arm 10 includes a ball joint 11 for connection with a steering knuckle (not shown) of a hub assembly and a pair of bushings 12, 13 for guiding the pivoting movement of the lower control arm 10 relative to the vehicle's frame (not shown). One of the bushings is a horizontal bushing 12 which is configured to pivot relative to the vehicle frame about longitudinally extending bolt (not shown). The other bushing 13 is a vertical bushing which is configured to pivot relative to the vehicle frame about a vertically extending bolt (not shown).
Referring now to FIGS. 2A-C, an conventional vertical bushing 13 is generally shown. As best shown in FIG. 2C, the conventional vertical bushing 13 has an outer metallic sleeve 14, which is press fit into an opening in the lower control arm 10 (shown in FIG. 1), a rubber cushion 15 and an inner metallic sleeve 16. The rubber cushion 15 extends radially between and interconnects the outer and inner metallic sleeves 14, 16. In operation, the inner metallic sleeve 16 pivots or twists relative to the outer metallic sleeve 14 during movement of the vehicle suspension, such as when the vehicle encounters a pot hole in the road. The rubber cushion 15 deforms elastically to allow the pivoting movement between these sleeves 14, 16 and absorbs/deforms due to a radial load. As such, during operation of the vehicle, the rubber cushion 15 is exposed to both a radial load and a twisting load motion. Exposure to the radial load and twisting motion leads to deterioration in the rubber cushion 15, thereby reducing the life of the vertical bushing 13.